Previous weapon location systems (as used throughout this Application, the term "system" refers to a combination, in one embodiment, of hardware, software, and/or firmware which cooperates to perform one or more applications or functions) used either a purely or substantially singular acoustical detection apparatus or techniques or a purely or substantially singular optical detection apparatuses and/or techniques to locate the source of hostile weapon fire. Due to the problems and/or drawbacks associated with purely acoustical and purely optical detection techniques or substantially pure or singular technology techniques, the present invention combines the two concepts or technologies in order to utilize the advantages and substantially eliminate the disadvantages of each technology. Applicant has found that the combination of acoustical and optical as well as other detection and tracking mechanisms greatly enhances the overall detection capability of the system. Applicant believes that there was, prior to Applicant's invention, no and/or substantially little or substantially no motivation to combine these techniques in the manner done by Applicant and which adequately achieved the results and/or goal of Applicant's invention.
Acoustical detection systems generally determine the direction and/or location of hostile weapon fire by measuring and/or calculating the various times of arrival of "sound" or acoustical energy generated by the hostile fire by the use of generally and equally spaced microphones formed or placed in a microphone array. Most prior acoustical hostile weapons fire detection and/or location systems are characterized by generally omnidirectional detection, only moderate accuracy and a substantially minimal false alarm rate. While such prior acoustical systems provide useful information for many applications, purely and/or substantially pure acoustical detection systems are not entirely appropriate for certain applications, such as applications involving the detection of the firing of supersonic and/or substantially supersonic projectiles, and the tracking of overhead "top attack" weapons. That is, supersonic projectiles arrive at the target prior to the arrival of the acoustical energy generated by the firing of these supersonic projectiles. Thus, an immediate counter-measure launch, necessary to destroy the incoming supersonic missiles, is generally not possible when a purely or singular acoustical system is used to detect the presence and/or location of such supersonic enemy fire. Additionally, it is well known that acoustical detection systems can have a relatively large error in the determination of the location of the hostile weapon. In the past, this was not really a problem since offensive countermeasures which were used to destroy the hostile weapon usually comprised one or more missiles which destroyed a relatively large area. This wide area of destruction mostly and adequately compensated for the errant location data provided by the acoustical detection and/or location systems. However, war has changed. Oftentimes snipers, located within relatively densely populated areas are now encountered. Hence, large destructive countermeasures, necessary to compensate for errant location calculations, are generally not appropriate since they might hurt or kill many innocent people and destroy many valuable and historic buildings and/or other structures.
Optical detection systems generally determine the location and/or direction of hostile weapons fire by observing and/or sensing the position of the optical energy released or generated when a weapon is discharged. Most optical systems are characterized by relatively high accuracy, relatively high amounts or levels of false alarms and a rather limited field of view. Purely optical systems are also of rather limited value in some ambient light conditions where distinguishing the flash of a weapon from false flashes or other types of visible radiation is difficult. Purely optical systems are also of rather limited value where a weapon is obstructed or outside of the optical system's field of view. Hence, these prior optical detection systems were used only in very few specific applications, mainly due to their relatively high false alarm rate. Heretobefore, only one type of these systems was used to determine/calculate the location of adverse weaponry. No one, prior to Applicant's discovery and/or invention, had realized the benefit of combining these two types of dissimilar systems in a manner which would overcome the drawbacks of each of these systems and provide a more robust system.
That is, Applicant was the first to realize that great accuracy and usefulness could be achieved by first using an acoustical system to determine the general location of the hostile weapons fire, a function that such prior acoustical systems performed relatively well, and then using an optical system or referring to or reviewing captured optical data in order to further refine the location within the field established by the acoustical system. In this manner, the relatively notorious "false alarms" associated with the optical systems could be minimized since only the optical data which emanates and/or is generated from the field of view formed or "fixed" by the acoustical technique would be reviewed. Moreover, the concomitant use of optical system data could allow even supersonic projectiles to be detected. This new combined system thus allows great accuracy which is necessary when detecting hostile weapons fire in cities and other areas in which greatly destructive missile counteroffensive apparatuses cannot be used.
Importantly, Applicant has discovered that the present invention is especially useful in detecting, tracking and countering attacks from overhead or "top attack" weapons. It is known that armored military vehicles generally have their strongest armor (greatest thickness) on their respective sides, and on their respective front and back surfaces. The armor covering the top and the bottom of armored vehicles is generally somewhat thinner, less protective, and generally more susceptible to failure than the armor on the sides of such vehicles. As a result, armored vehicles are generally known and/or thought to be more difficult to attack using weapons that have horizontal trajectories, and are more vulnerable to weapons following and/or exhibiting steep travel trajectories and weapons which may be launched or fired from directly above these vehicles. Until relatively recently, the "threat" weapons or the weapons used to attach armored vehicles have been almost exclusively horizontal trajectory weapons.
However, to exploit the higher vulnerability of the "topside" armor of military armored mobile vehicles, new weapons have been developed. Generally, these weapons can direct shaped charges and launch projectiles towards armored vehicles from a location directly above the vehicle.
A diagram of the travelling and/or firing trajectory or path 102 of one such weapon and the significant events of its arming sequence is shown in FIG. 12. As illustrated in FIG. 12, the overhead weapon 120 comprises a delivery device 100, typically a 155 mm artillery projectile, which is initially launched and carries or "delivers" the overhead or "top attack" weapon portion 104 to a point approximately 1200 meters or more above the target vehicle 118. At this point, top attack weapon portion 104 generally comprising a "package" containing two submunition "packages" 106, 108 is expelled from the delivery projectile 100 by a small explosive charge (i.e., "the main event"). This is followed almost immediately by a first "band cutter" event where a small explosive (not shown) cuts a steel band 109 usually connecting packages 106, 108, effective to separate the two submunition packages 106, 108. Each package relatively immediately deploys a parachute-like fabric decelerator 110 (e.g., a "Rapid Air Inflatable Decelerator" ("RAID")), to slow the horizontal speed of each submunition 106, 108 from the horizontal launch speed of approximately mach 1 to essentially zero. This causes each submunition 106, 108 to fall along a vertical trajectory. After each of the two submunitions 106, 108 has slowed to a vertical trajectory, a small explosive charge in each submunition (not shown) performs a second band cutter task that is effective to cause the deployment of a second parachute-like device 112 (e.g., a Vortex Ring Parachute ("VRP")), from each submunition package. The VRP provides the platform for vehicle target acquisition and attack by the submunition. At this point, each submunition will scan for a target (i.e., an armored vehicle 118) in a predetermined area below the submunition using heat sensing, image recognition or another suitable technology. Upon locating a viable target, each submunition 106, 108 will fire a projectile or explosive device (not shown) upon the target. The entire top attack sequence from "the main event" to the firing by submunitions 106, 108 may take as long as 30 to 45 seconds.
Each of the afore-described events (i.e., the main event, the first band cutter event, and the second band cutter event) generates an acoustical event. The main event will also typically generate an optical flash that is visible in the mid-wave IR band. Various falling objects have also been observed with a mid-wave IR camera. The sensor fusion system of the present invention generally allows for generally reliable detection, tracking and countermeasure accuracy and results of such top-attack weapons which emit various acoustical and optical signals.
There is therefore a need for, and it is a principal object of this invention to provide, a weapon and/or hostile weapons firing location and localization system which overcomes the aforementioned drawbacks of the prior substantially purely acoustical and substantially purely optical detection systems and which, in fact, combines the advantages and the techniques of the two systems to achieve a system characterized by general omnidirectional detection, a relatively low false alarm rate, relatively high accuracy and relatively immediate counter-measure capability. In essence, Applicant has discovered that one may utilize the accuracy of infrared systems in combination with "gross" type location data specified by the acoustical systems to provide a very desirable "fused" system. Applicant has further discovered that such a combination of systems can be further improved by using various tracking technologies which will allow a target to detect an overhead attack, take defensive action and direct a countermeasure. As used in this Application, the terms "location" and "localization" each mean the location of an entity (e.g. hostile weapons fire) as well as the processes to locate the firing entity. Thus, these words may be used interchangeably.